Pretty obviously a bad joke and a bad idea IMO. I did not personally downvote, but I think it deserves its current score.
Look at the timeline of the events. The switches were shut off, noticed to be shut off, and restored to the proper position within 10 seconds with the current system. Insufficient notification that the switches have been turned off was clearly not a problem in need of a solution. It would be slower and more challenging to understand an automated verbal announcement than the surely extremely obvious sudden lack of thrust and all engine dials rapidly dropping to zero.
So it wouldn't contribute at all to solving this particular case, would only be a slightly annoying distraction in the more normal case of normal aircraft shut-down after completing its flights, and would be a potentially hazardous distraction in the intended emergency case of engine is on fire and fuel must be cut off immediately, where there's probably a bunch of other extremely important and urgent things to pay attention to and do other than a silly automated warning telling you what you just did.